Catalytic composition and process for the alkylation and/or transalkylation of aromatic compounds

Abstract

A catalytic composition is described for the alkylation and / or transalkylation of aromatic hydrocarbons consisting of beta zeolite, as such or modified by the isomorphous substitution of aluminum with boron, iron or gallium or by the introduction of alkaline and / or earth alkaline metals following an ion-exchange process, and an inorganic ligand, wherein the extrazeolite porosity, i.e. the porosity obtained by adding the mesoporosity and macroporosity fractions present in the catalytic composition itself, is such that a fraction of at least 25% is composed of pores with a radius higher than 100 ANGSTROM , said composition being characterized by a total volume of extrazeolitic pores greater than or equal to 0.80 ml / g.

Description

FIELD OF THE INVENTIONThe present invention relates to catalytic compositions consisting of beta zeolite (as such or modified) and a ligand, characterized by particular porosity characteristics, which can be used in processes for the alkylation of aromatic hydrocarbons with light olefins, in particular benzenes with C.sub.2 -C.sub.4 olefins and more specifically benzene with ethylene to give ethylbenzene and benzene with propylene to give cumene. The catalytic composition of the present invention can also be used in the transalkylation of aromatic hydrocarbons with polyalkylated aromatic hydrocarbons, especially benzene with diethylbenzene, and possibly triethylbenzene, to give ethylbenzene and benzene with diisopropylbenzene, and possibly triisopropylbenzene, to give cumene.DESCRIPTION OF THE BACKGROUNDFormer processes, still widely used in the petro-chemical industry for the production of alkylaromatics, and in particular cumene and ethylbenzene, comprise the use of a catalyst bas...

AI Technical Summary

Problems solved by technology

These processes however create problems relating to environment and safety; in fact the use of these catalysts is particularly problematical due to corrosion, the by-production of toxic organic products and the disposal of the exhausted catalysts.

This type of zeolitic system however, perhaps owing to channels which are too small, only allows the production of cumene with rather low selectivities.

The necessity for high mechanical characteristics is much greater in the case of regenerable catalysts which must frequently undergo thermal regeneration treatment, which causes strong structural stress.

In case of thermal regenerations carried out "off-site", the use of a catalyst with insufficient mechanical characteristics would lead to considerable losses in material during the numerous charging and discharging of the exhausted and regenerated catalyst.

This aspect is therefore of primary importance if the regenerable catalyst is used in existing industrial plants, where it may not be possible to carry out the thermal regeneration in situ.

The achievement of excellent mechanical characteristics is however generally hindered by the necessity of maintaining certain porosity characteristics which are necessary for the reaction in which the catalyst is used.

Generally however, the results obtained by varying the parameters of the process are accompanied by a significant drop in the mechanical charactertistics if the increase in the total EPV extrazeolite porosity is significant.

The addition of substances suitable for creating porosity in the subsequent calcination phase of the catalyst generally produces more evident results in terms of an increase in EPV, which is obtained however by increasing the porosity generally in the highest mesoporosity and macroporosity zone; this causes a drastic deterioration in the mechanical characteristics of the catalyst, mainly in the case of materials which have a percentage of binder for example of between 20 and 50% by weight as in the case of zeolitic catalysts.

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